Pin joints for machinery generally fall into two categories. Dynamic joints where structural members move relative to each other and static joints where the structural members do not move. When dynamic joints are present, they may move back and forth making oscillatory motion. As can be imagined, this creates friction and wear that may limit the life of the pin joint. Consequently, the art has developed schemes to limit this friction and prolong the life of the pin joint.
Oscillating pin joints in construction and mining equipment typically include a pin and a mating bearing that is press fit into the surrounding structure. The joint comprises a middle structural member, often referred to as the bearing housing, and outside structural members on either side of the bearing housing. The bearing housing and the outside structural members will often rotate relative to each other a certain amount when the linkages of the boom of the machine extend. This rotation is reversed when the linkages of the machine retract. Hence, these joints have an oscillating rotating motion.
Lubricant is typically employed in these joints to reduce friction and prolong the life of the joint. The seam formed between the outside structural member and the bearing housing needs to be sealed to prevent the loss of the lubricant while still allowing the oscillating motion to occur between the bearing housing and the outside structural member. Duo cone seals are often used in such joints that employ two symmetrically arranged metal seal members that are urged into contact with each other using resilient load rings. However, it has been determined that such duo cone seals are better suited for applications where continuous rotation in one direction occurs rather than reversing or oscillating motion.
As can be imagined, seal failure or seals having a limited life may increase the amount of maintenance that is needed to keep a machine up and running. This may lead to increased maintenance costs and lost profits for a construction, earth moving or mining endeavor or the like. Therefore, it is desirable to develop a dynamic oscillating pin joint for machinery that is more robust than has yet been devised.